The present invention relates to radio frequency power amplifiers.
Portable devices such as laptop personal computers. Personal Digital Assistant (PDA) and cellular phones with wireless communication capability are being developed in ever decreasing size for convenience of use. Correspondingly, the electrical components thereof must also decrease in size while still providing effective radio transmission performance. However, the substantially high transmission power associated with radio frequency (RF) communication increases the difficulty of miniaturization of the transmission components.
A major component of a wireless communication device is the power amplifiers (PA). A PA can he fabricated on a semiconductor integrated circuit (IC) chip to provide signal amplification with substantial power. The power amplifier chip can be interconnected with certain off-chip components such as inductors, capacitors, resistors, and transmission lines for operation controls and for providing impedance matching to the input and output RF signals.
One significant challenge for power amplifiers is power consumption. As RF devices are used in longer distances and broader frequencies, the RF devices can consume power at increased rates. Batteries of the RF devices often need to be frequently recharged. Several attempts have been made to improve power amplifiers' power consumption. A power amplifier using so called “Doherty Technique” includes a plurality of serially connected power amplifiers. Another attempt utilizes a number of power amplifiers arranged in a parallel circuit. Another design attempts to reduce power amplifiers' power consumption using quadrature balanced amplifiers. These designs, however, usually cannot provide high quality signals in a wide output power range and a wide frequency range.